1. Field of Invention
The present invention relates to an image compensation method and a image acquisition device using the same, and more particularly to an image compensation method capable of reducing a noise and a image acquisition device using the same.
2. Related Art
With the popularity of image acquisition devices, more and more users have opportunities to take photos. For beginners, the captured images often become blurred due to handshakes during shooting. To solve this problem, the following methods for improvement are proposed. In a first method, a shake detection mechanism of a lens or camera body is used to correct the shake during shooting. In a second method, the International Standard Organization (ISO) is increased when shooting, because a higher ISO can shorten the shutter time and meanwhile achieves the same exposure as that obtained in a longer shutter time at a lower ISO.
The defect of the first method lies in that the shake detection mechanism requires additional hardware equipment, which increases the manufacturing cost of cameras. The second method does not require additional hardware equipment, so the manufacturing cost of the second method is lower than that of the first method. However, the defect of the second method lies in that noise often appears in images captured at a high ISO, especially when the ISO is increased to 800 or higher.
The noise mainly originates from statistical errors in a process when a charge coupled device (CCD) or a complementary metal-oxide semiconductor (CMOS) in the image acquisition device receives photons in light and converts the photons into electronic signals. The material, quantum effect, and signal amplification of the photosensitive element are also sources of the noise. In addition, the photosensitive element may generate electrons and holes due to the temperature variation in a lightless environment, which is referred to as a dark current effect. The additional electrons cause false determination of a signal processor, resulting in the generation of noise. The dark current increases with the rise of the ambient temperature, and is even higher after the temperature of the photosensitive element rises after long use.
Therefore, a method for processing digital images by low ISO and pixel binning is also proposed. The pixel binning is to combine surrounding pixels of a target pixel, so as to improve the brightness of the target pixel. Although such a method of pixel binning can prevent the noise caused by the increase of the ISO, the resolution of the digital image is lowered after binning the surrounding pixels.